The Pathology Core Component supports all of the program projects by providing anatomic and hematopathology data. Beyond the usual activities of a diagnostic pathology service, this component provides special attention to collection of research data which is then available to all investigators in the grant. Pathology also coordinates extensive specimen collection from biopsies and autopsies needed to carry out the research proposals, including preparation of frozen tissues and tissue culture specimens, and support for immunology, virology, and molecular biology through immunohistochemical and DNA hybridization techniques and other histological methods. Research support activities include: 1) extensive autopsies on all autologous marrow transplant recipients, 2) continued studies of lymph node and thymus gland tissue in autologous recipients in comparison to those of allogeneic recipients to further elucidate the differences attributable to allograft defects, 3) continued study of autologous skin rashes for immunobiological mechanisms, particularly by way of protocol 568 and comparison to skin biopsies of patients undergoing treatment with IL-2/LAK, GM-CSF and other cytokines, 4) continued study and development of viral probes and PCR methodology for the study of viral infections, including the development of a 4 virus screen for diagnosis, 5) systematic study of marrow damage correlates for the cytokine studies of Project 14, and 6) continued study of veno-occlusive disease in autologous recipients via liver biopsy, especially transvenous biopsy techniques.